In refining crude petroleum, various naphtha streams are produced in additional to the gasoline pool. The naphtha streams, which contain valuable compounds such as ethylene and propylene, are then often times introduced into a naphtha cracker to produce products such as polyethylene and polypropylene. The naphtha cracker, in turn, produces various streams, including a C4 raffinate stream that contains isobutene, butadiene, isobutylene, and other C4 molecules, many of which are also very useful. For instance, butadiene can be polymerized and used in various rubbers, and isobutylene is useful as a starting material for many industrial compounds, including tert-butyl-phenols.
However, to produce tert-butyl phenols from isobutylene typically involves a “pure” isobutylene, while the isobutylene from the raffinate stream contains varying amounts of butenes and butanes in addition to other alkanes and alkenes ranging from C2 to C5. When reacting the C4 raffinate stream with phenol, the butenes, particularly the 1-butene and the 2-butene, competitively react with the phenol to produce undesirable sec-butyl phenols in addition to the desirable tert-butyl phenols. Separating the sec-butyl phenols from the tert-butyl-phenols is costly and adversely affects the yield the desired products.
Conventional processes for producing tert-butyl phenols from an isobutylene-containing C4 raffinate stream typically involve introducing methanol, or another alcohol, into the C4 stream to react create an alkyl-tert-butyl ether intermediate that is further decomposed to make high-purity isobutylene, which can then be reacted with phenol to produce the tert-butyl phenols. The additional step of adding methanol significantly increases the costs of producing tert-butyl phenols, and creates another undesirable byproduct. Besides the additional expense, the additional byproducts are unattractive for environmental reasons. Various other methods of producing tert-butyl phenols are disclosed in U.S. Pat. No. 4,166,191, but these processes, like the conventional methods, utilize extra steps and expensive materials.
What is needed in the art is a method of producing a tert-butyl phenol by selectively reacting a phenol with an isobutylene-containing C4 raffinate stream so that the isobutylene reacts with the phenol while none, or very few, of the butenes present in the C4 raffinate stream are reacted with the phenol. This invention answers that need.